U.S. patent application number 13/981321 was filed with the patent office on 2013-11-28 for base station and resource allocation method of mobile communication system.
This patent application is currently assigned to NTT DOCOMO, INC.. The applicant listed for this patent is Hiroyuki Ishii, Mikio Iwamura, Rika Kitou, Kohei Kiyoshima, Yoshiaki Ofuji, Naoto Ookubo, Anil Umesh. Invention is credited to Hiroyuki Ishii, Mikio Iwamura, Rika Kitou, Kohei Kiyoshima, Yoshiaki Ofuji, Naoto Ookubo, Anil Umesh.
Application Number | 20130315182 13/981321 |
Document ID | / |
Family ID | 47072003 |
Filed Date | 2013-11-28 |
United States Patent
Application |
20130315182 |
Kind Code |
A1 |
Kitou; Rika ; et
al. |
November 28, 2013 |
BASE STATION AND RESOURCE ALLOCATION METHOD OF MOBILE COMMUNICATION
SYSTEM
Abstract
A base station of a mobile communication system includes a
scheduler that generates uplink grant information indicating that
uplink radio resources are allocated to less than or equal to a
first multiplexing number of units of user equipment, a transmitter
that transmits a control signal including the uplink grant
information to the user equipment, and a receiver that receives an
uplink signal which is transmitted by the user equipment. When a
second multiplexing number being less than the first multiplexing
number or more units of the user equipment exist which transmit
periodically generated periodic data, and when the user equipment
exists which transmits non-periodic data generated at non-periodic
timing, the scheduler generates the uplink grant information
indicating that the uplink radio resources are allocated to the
second multiplexing number of the units of the user equipment that
transmit periodic data and to the user equipment that transmits
non-periodic data.
Inventors: |
Kitou; Rika; (Chiyoda-ku,
JP) ; Kiyoshima; Kohei; (Chiyoda-ku, JP) ;
Ookubo; Naoto; (Chiyoda-ku, JP) ; Ishii;
Hiroyuki; (Chiyoda-ku, JP) ; Ofuji; Yoshiaki;
(Chiyoda-ku, JP) ; Iwamura; Mikio; (Chiyoda-ku,
JP) ; Umesh; Anil; (Chiyoda-ku, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kitou; Rika
Kiyoshima; Kohei
Ookubo; Naoto
Ishii; Hiroyuki
Ofuji; Yoshiaki
Iwamura; Mikio
Umesh; Anil |
Chiyoda-ku
Chiyoda-ku
Chiyoda-ku
Chiyoda-ku
Chiyoda-ku
Chiyoda-ku
Chiyoda-ku |
|
JP
JP
JP
JP
JP
JP
JP |
|
|
Assignee: |
NTT DOCOMO, INC.
Tokyo
JP
|
Family ID: |
47072003 |
Appl. No.: |
13/981321 |
Filed: |
April 4, 2012 |
PCT Filed: |
April 4, 2012 |
PCT NO: |
PCT/JP2012/059265 |
371 Date: |
July 24, 2013 |
Current U.S.
Class: |
370/329 |
Current CPC
Class: |
H04W 72/1247 20130101;
H04W 72/0406 20130101; H04W 72/1289 20130101 |
Class at
Publication: |
370/329 |
International
Class: |
H04W 72/04 20060101
H04W072/04 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 28, 2011 |
JP |
2011-101948-2011 |
Claims
1. A base station of a mobile communication system, the base
station comprising: a scheduler that generates uplink grant
information, wherein the uplink grant information indicates that
uplink radio resources are allocated to less than or equal to a
first multiplexing number of units of user equipment; a transmitter
that transmits a control signal including the uplink grant
information to the user equipment; and a receiver that receives an
uplink signal, wherein the uplink signal is transmitted by the user
equipment in accordance with the uplink grant information, wherein,
when a second multiplexing number or more units of user equipment
exist which transmit periodic data which is periodically generated,
when user equipment exists which transmits non-periodic data which
is generated at non-periodic timing, and when the second
multiplexing number is less than the first multiplexing number, the
scheduler generates the uplink grant information, the uplink grant
information indicating that the uplink radio resources are
allocated to the second multiplexing number of the units of the
user equipment that transmit periodic data and to the user
equipment that transmits non-periodic data.
2. The base station according to claim 1, further comprising: a
user multiplexing number controller that controls the second
multiplexing number depending on the number of the units of the
user equipment which transmit the periodic data in a cell of the
base station.
3. The base station according to claim 1, wherein, when the
scheduler allocates the radio resources to the units of the user
equipment up to the first multiplexing number in accordance with an
order of priority of first user equipment that transmits the
periodic data, second user equipment that transmits the
non-periodic data, third user equipment that transmits the periodic
data which is not for retransmission, and fourth user equipment
that transmits the non-periodic data which is not for the
retransmission, and when a number of the units of the first user
equipment and the third user equipment is greater than the second
multiplexing number, a total number of the units of the first user
equipment and the third user equipment to which the radio resources
are allocated is limited to be the second multiplexing number.
4. The base station according to claim 1, wherein, when the second
multiplexing number or more units of the user equipment that
transmit the periodic data exist, and when a third multiplexing
number of units of the user equipment that transmit the
non-periodic data exist, if the radio resources which can be
allocated are remaining, subsequent to allocating the radio
resources to the second multiplexing number of the units of the
user equipment and to the third multiplexing number of the units of
the user equipment, the scheduler generates the uplink grant
information indicating that the uplink radio resources are
allocated to more than the second multiplexing number of the units
of the user equipment that transmit the periodic data and to the
third multiplexing number of the units of the user equipment that
transmit the non-periodic data.
5. The base station according to claim 1, wherein the periodic data
is voice data.
6. A resource allocation method comprising: a step of generating
uplink grant information, wherein the uplink grant information
indicates that uplink radio resources are allocated to less than or
equal to a first multiplexing number of units of user equipment; a
step of transmitting a control signal including the uplink grant
information to the user equipment; and a step of receiving an
uplink signal, wherein the uplink signal is transmitted by the user
equipment in accordance with the uplink grant information, wherein,
when a second multiplexing number or more units of user equipment
exist which transmit periodic data which is periodically generated,
when user equipment exists which transmits non-periodic data which
is generated at non-periodic timing, and when the second
multiplexing number is less than the first multiplexing number, the
step of generating uplink grant information generates the uplink
grant information, the uplink grant information indicating that the
uplink radio resources are allocated to the second multiplexing
number of the units of the user equipment that transmit periodic
data and to the user equipment that transmits non-periodic data.
Description
TECHNICAL FIELD
[0001] The present invention relates to a base station and a
resource allocation method of a mobile communication system.
BACKGROUND ART
[0002] As a technique for improving frequency utilization
efficiency of a mobile communication system, there is frequency
scheduling.
[0003] For a case of a dynamic scheduling method, radio resources
are dynamically allocated to a user, depending on priority
corresponding to a type of data and whether a radio channel state
is good. For example, a determination is made for every subframe of
1 ms as to which radio resource is to be allocated to which user.
Since a manner of allocating the radio resources to the user
frequently changes, the radio resources can be flexibly
utilized.
[0004] There are various types of data which are exchanged by a
user. The various types of data include data such that an amount of
the data is small but latency of the data is restricted to be
small, such as voice data or a voice packet (VoIP); and data such
that an amount of the data is large but latency of the data is not
restricted to be so small, such as data communication. For a case
of the voice data (VoIP), a small amount of data is periodically
generated. When scheduling is performed for such voice data in
accordance with the dynamic scheduling method, it is required to
specify a radio resource for each voice data, which is the
periodically generated small amount of data, on a one-by-one basis.
In this case, signaling overhead which is required for notifying
users of the radio resources becomes large relative to the whole
data to be transmitted. Thus, it is possible that the utilization
efficiency of the radio resources is lowered.
[0005] A semi-persistent scheduling (SPS) method is a method which
can address such a concern. For a case of the semi-persistent
scheduling method, allocation of radio resources for one time is
applied not only to one subframe, but also to a subsequent great
number of subframes. Namely, by periodically allocating fixed radio
resources, the overhead can be reduced which is required for
signaling of the radio resources. Accordingly, if all units of user
equipment of the mobile communication system conform to the
semi-persistent scheduling (SPS) method, the above-described
concern can be resolved by using the SPS for the voice data.
[0006] However, since the semi-persistent scheduling (SPS) method
is not mandatory for the 3GPP standards, it is not always true that
user equipment of the mobile communication system conforms to the
semi-persistent scheduling method. For the case where not all the
units of user equipment conform to the SPS, it may be necessary to
perform allocation of the radio resources by the dynamic scheduling
method after all. However, in this case, it may be required to
specify radio resources for each voice data, which is the
periodically generated small amount of data, on a one-by-one basis.
Consequently, the overhead may become large. In addition, a problem
of concern is that the radio resources may not be effectively
utilized.
[0007] Here, an amount of the overhead is not constant. For a case
of an LTE-based mobile communication system, one through three
symbols are allocated to a control signal (e.g., a PCFICH, a PHICH,
and a PDCCH) (overhead) in one subframe, which is formed of ten or
more symbols. Such an amount of the overhead varies depending on a
number of users in a cell or a radius of a cell. The greater the
number of the users in the cell; a traffic amount of data; a number
of simultaneously multiplexed users per one subframe; the radius of
the cell; or the like is, the greater the amount of the overhead
becomes. That can be a cause of lowering throughput. Non-Patent
Document 1 discloses the LTE-system, for example.
[0008] In the LTE-based mobile communication system, scheduling is
performed for every subframe (TTI) of 1 ms, and control information
(e.g., the PDCCH) indicating content of the allocation of the radio
resources is transmitted to user equipment. After a predetermined
time period is elapsed (e.g., 4 ms after the reception of the
control information), the user equipment transmits an uplink signal
(PUSCH) using the radio resources which are indicated by the
control information. Suppose that the number of the users to which
the radio resources can be assigned is N in one subframe. Since the
voice data is periodically generated, the period is denoted by T.
In this case, the number of the users who can simultaneously use a
voice service (i.e., a voice capacity) is N.times.T. For example,
if N=3, and T=20 ms, the voice capacity is equal to 3.times.20=60
people.
[0009] FIG. 1 shows a situation where various units of user
equipment (UE1-UE60) transmit voice data within 20 ms. As described
above, since a data volume of the voice data is small, if an uplink
subframe is occupied by users who transmit the voice data, a part
of a usable radio resource remains, and it is wasted. Since the
voice data is to be transmitted and received in real time, the
voice data has higher priority relative to that of data other than
the voice data. Accordingly, when users who communicate voice data
and users who communicate data other than the voice data coexist,
radio resources are preferentially allocated to the users of the
voice data, and as shown in FIG. 1, remainders of the radio
resources are generated, thereby degrading the utilization
efficiency of the radio resources. In this case, if it is possible
to increase a number of the users in the downlink to whom the
content of the allocation of the radio resources can be
communicated, such a concern may be resolved. However, in order to
achieve this, it is necessary to modify the standard specification
that defines a format of a downlink signal. Thus, it is not
easy.
RELATED ART DOCUMENT
Non-Patent Document
[0010] Non-Patent Document 1: 3GPP TS36.300 V8.11.0 (2009-12)
SUMMARY OF THE INVENTION
[0011] The base station according to one embodiment is a base
station of a mobile communication system including a scheduler that
generates uplink grant information, wherein the uplink grant
information indicates that uplink radio resources are allocated to
less than or equal to a first multiplexing number of units of user
equipment; a transmitter that transmits a control signal including
the uplink grant information to user equipment; and a receiver that
receives an uplink signal, wherein the uplink signal is transmitted
by the user equipment in accordance with the uplink grant
information. When a second multiplexing number or more units of
user equipment exist which transmit small data, and when user
equipment exists which transmits large data, wherein the second
multiplexing number is less than the first multiplexing number, the
scheduler generates the uplink grant information, wherein the
uplink grant information indicates that the uplink radio resources
are allocated to the second multiplexing number of the units of the
user equipment that transmit periodic data and to the user
equipment that transmits large data.
EFFECT OF THE PRESENT INVENTION
[0012] According to one embodiment, when the radio resource is to
be allocated to the small data, the uplink radio resource can be
effectively utilized.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a diagram showing a situation where various units
of user equipment are transmitting voice data;
[0014] FIG. 2 is a functional block diagram of an eNodeB which is
used in an embodiment;
[0015] FIG. 3A is a flowchart showing an operation example in the
eNodeB;
[0016] FIG. 3B continues the flowchart showing the operation
example in the eNodeB;
[0017] FIG. 4 is a diagram schematically showing an uplink subframe
when a radio resource is allocated according to the embodiment;
[0018] FIG. 5 is a diagram schematically showing an uplink subframe
when a radio resource is allocated according to the embodiment;
[0019] FIG. 6A is a flowchart showing an operation example
according to a modified example;
[0020] FIG. 6B continues the flowchart showing the operation
example according to the modified example;
[0021] FIG. 7 is a diagram showing that a radio resource is
allocated to units of user equipment;
[0022] FIG. 8 is a diagram for illustrating another modified
example;
[0023] FIG. 9A is a flowchart showing an operation example
according to the other modified example;
[0024] FIG. 9B continues the flowchart showing the operation
example according to the other modified example; and
[0025] FIG. 9C continues the flowchart showing the operation
example according to the other modified example.
EMBODIMENTS FOR CARRYING OUT THE INVENTION
[0026] In an embodiment which is explained below, a multiplexing
number of voice users who transmit periodic data, such as voice
data, is limited to a maximum voice user multiplexing number, which
is in principle less than a "maximum user multiplexing number" in a
subframe. Here, for the "maximum user multiplexing number," one of
two cases can be considered, namely, either a case where it is
fixedly defined or a case where it is defined to be a limit number
of multiplexing PDCCHs. Further, for a case where a resource of a
channel for transmitting control information for specifying the
radio resource (PDCCH) remains, voice users who are greater in
number than the maximum voice user multiplexing number may be
multiplexed. By doing this, the frequency utilization efficiency is
improved. The maximum voice user multiplexing number may be
dynamically changed based on a number of the voice users or a
utilization rate of the control channel (PDCCH) of a voice bearer.
For example, for a case where the maximum user multiplexing number
is four, the maximum voice user multiplexing number may be set to
be three, and the maximum multiplexing number of data other than
voice data may be set to be one, during busy hours. Alternatively,
during non-busy hours, the maximum voice data multiplexing number
may set to be two, and the maximum non-voice data multiplexing
number may be set to be two. For simplicity of an explanation, an
example is explained where voice data or a voice packet is
utilized. However, the voice data or the voice packet is merely an
example. The embodiment may be applied to all bearers for which
only small data is generated. In the embodiment, a multiplexing
number of voice users is limited to the maximum voice user
multiplexing number, which is less than the maximum user
multiplexing number. In principle, the radio resource is not
allocated to voice users in excess of that number. The voice data
includes voice data by retransmission (which consumes a PDCCH) as
well as voice data of first transmission. In the embodiment, when
the radio resource is allocated to the maximum voice user
multiplexing number of the voice users, and subsequently there are
no non-voice users who transmit data other than the voice data, or
subsequent to allocating the radio resource to non-voice users, it
is possible that radio resource remains. In such a case, the radio
resource is allocated to voice users in excess of the maximum voice
user multiplexing number.
[0027] Hereinafter, the embodiment is explained from the following
perspectives.
[0028] 1. eNodeB (base station)
[0029] 2. Operation example
[0030] 2.1 A case where voice users and non-voice users coexist
[0031] 2.2 A case where only voice users exist
[0032] 3. Modified example
[0033] 3.1 Modified example where retransmission is considered
[0034] 3.2 Modified example where PDCCH resource allocation amount
is considered
Embodiment
1. eNodeB (Base Station)
[0035] FIG. 2 shows a functional block diagram of an eNodeB (base
station), which is used in the embodiment. In FIG. 2, among
processors that achieve various functions included in the eNodeB of
a mobile communication system, there are shown processors which are
particularly related to the embodiment. For convenience of the
explanation, the base station shown in the figure is, for example,
an eNodeB of an LTE-based mobile communication system. The base
station may be a base station of another mobile communication
system. FIG. 2 shows an uplink signal receiver 201; an uplink
quality measurement unit 203; a user multiplexing number controller
205; a scheduler 207; a downlink signal generator 213; and a
downlink signal transmitter 215.
[0036] The uplink signal receiver 201 receives an uplink signal
from user equipment (UE), and the uplink signal receiver 201
converts it into a base band signal. Accordingly, the uplink signal
receiver 201 includes a function of filtering a received radio
signal; a function of converting an analog signal into a digital
signal; a function of demodulating data of the received signal; and
a function of channel decoding the received signal. In general, an
uplink signal includes a control signal, a pilot signal, a data
signal, and the like. Here, the user equipment (UE) may be any
suitable communication device that communicates with the eNodeB
through a radio link. The user equipment may be a mobile terminal
or a fixed terminal. Specifically, the user terminal (UE) may be a
mobile phone, an information terminal, a high-performance mobile
phone, a smart phone, a tablet computer, a personal digital
assistant, a mobile computer, or the like. However, the user
terminal (UE) is not limited to these.
[0037] The uplink quality measurement unit 203 measures an uplink
radio channel condition. The uplink radio channel condition may be
derived from a received level of the pilot signal included in the
received uplink signal. The received level may be expressed in
terms of any suitable quantity which is known to a person skilled
in the art. As an example, the received level is broadly defined to
be a quantity that represents whether a radio channel condition is
good, regardless of whether it is an instantaneous value or an
average value. For example, the received level may be represented
by a received signal code power RSCP, reference signal received
power RSRP, a path loss, SNR, SIR, SINR, Ec/N.sub.0, RSCP, RSRQ,
and/or E.sub.b/N.sub.0. The desired wave of RSCP, SNR, SIR, or SINR
may be power of a shared data channel (PUSCH, PDSCH), or power of
the pilot signal (a sounding reference signal (SRS), a demodulation
reference signal (DMRS), a cell-specific reference signal, or a
user-specific reference signal).
[0038] The user multiplexing number controller 205 controls the
maximum voice user multiplexing number N.sub.VOICE, which is less
than the maximum user multiplexing number N.sub.MAX, and the user
multiplexing number controller 205 transmits it to the scheduler
207. The maximum user multiplexing number N.sub.MAX is the maximum
number of units of user equipment which can transmit data on the
same uplink subframe. The maximum voice user multiplexing number
N.sub.VOICE is the maximum number of units of user equipment which
can transmit synchronization data on the same uplink subframe.
Periodic data is periodically generated data. Typically, it is
voice data. In the explanation below, for simplicity, the
explanation is given while exemplifying a case where a user
communicates voice data. However, the embodiment is not limited to
the voice data, and the embodiment may be applied to any
communication where small-sized data is periodically generated.
Even if a bearer is not periodic, the embodiment can be applied to
the bearer, provided that the bearer is such that only low rate
data (a small sized packet) is generated for the bearer. The
maximum user multiplexing number N.sub.MAX is kept to be a constant
value. The maximum voice user multiplexing number N.sub.VOICE may
be controlled to be varied, or it can be maintained to be constant.
When it is controlled to be varied, for example, it can be
controlled such that the maximum user multiplexing number N.sub.MAX
is 4 and the maximum voice user multiplexing number N.sub.VOICE is
set to be 3, 2, or 1, depending on the number of the users who
transmit voice data within a cell (when the number of the users who
transmit the voice data is large, the maximum voice user
multiplexing number N.sub.VOICE is 3, and when the number of the
users who transmit the voice data is small, the maximum voice user
multiplexing number N.sub.VOICE is 1). Specific numerical values of
the maximum user multiplexing number N.sub.MAX and the maximum
voice user multiplexing number N.sub.VOICE are merely examples, and
other values may be used. Further, the maximum voice user
multiplexing number N.sub.VOICE may be controlled, depending not
only on the number of the voice users, but also on a traffic
amount.
[0039] Here, the number of the users who transmit the voice data
may be set to be the number of the users for whom voice bearers are
established. Alternatively, the number of the users who transmit
the voice data may be set to be the number of the users who are in
a talk-spurt period, among the users for whom the voice bearers are
established. In general, when a person performs a conversation, a
talk-spurt period, which is a generation interval, and a silent
period, which is a voiceless interval, are alternately generated.
In the talk-spurt period, voice data is generated at a constant
period of 20 ms, for example.
[0040] The scheduler 207 determines priority of a user (user
equipment) who has data to be communicated. For example, scheduling
coefficients may be calculated, and users may be selected in an
order of the scheduling coefficients. It is not limited to the
method where the scheduling coefficients are calculated and the
priority is determined. The priority may be calculated by any
algorithm, provided that the priority is determined such that the
voice bearers are preferentially scheduled. When the scheduler 207
determines the priority by calculating the scheduling coefficients,
the scheduler 207 allocates an uplink radio resource to user
equipment based on a logical channel group (Logical Channel Group:
LCG) and the scheduling coefficient. The scheduling coefficient may
be calculated by any suitable method based on presence or absence
of a request for scheduling, the logical channel group (LCG), an
instantaneous data rate, and an average data rate, for example. The
logical channel group LCG is the priority in accordance with a
logical channel onto which specific data is mapped. For example,
the priority of the LCG which is associated with voice data is
higher than that of the LCG which is associated with data of data
communication. The scheduling coefficients may be calculated, for
example, by a Max C/I method, or a proportional fairness
method.
[0041] The eNodeB receives a notification of a quality of service
(QoS) class indicator (QCI: Quality of Service Class Indicator)
regarding information which is communicated by the user from a core
network. This QCI represents priority on a type of traffic. The
eNodeB multiplies a factor, which corresponds to the QCI, with the
scheduling coefficient of the user, so that the scheduling
coefficient takes a value corresponding to the priority of the QCI.
Further, based on the QCI, for example, frequency of the scheduling
can be controlled in accordance with the QCI. The scheduling is
performed based on a plurality of the logical channel groups (LCG)
corresponding to the QCI. For a case of a user having data which
belongs to a low priority LCG and data which belongs to a high
priority LCG, a radio resource is allocated from the data which
belongs to the high priority LCG. Here, the embodiment can be
applied not only to a case where the radio resource is allocated
based on the scheduling coefficient, but also it can be broadly
applied to a case where a voice bearer is allocated to a radio
resource based on any preferential algorithm, differently from the
scheduling coefficient.
[0042] The scheduler 207 preferentially allocates a radio resource
to a user whose value of the scheduling coefficient is relatively
large (or who is deterministically determined to have high
priority). A method of allocating the radio resources in the uplink
is sent to the user equipment as uplink grant information by a
control signal. Detailed operations are described later. However,
in general, when there exist the voice data multiplexing number
N.sub.VOICE of units or more units of user equipment that transmit
voice data, and there exists user equipment that transmits
non-periodic data which is not the voice data, the scheduler 207
allocates uplink radio resources to user equipment which transmits
voice data and whose voice data multiplexing number is N.sub.VOICE,
and the scheduler 207 allocates the uplink radio resources to one
or more units of user equipment that transmit non-periodic
data.
[0043] When the scheduler 207 allocates radio resources, the radio
resources are allocated to a number of units of user equipment in
accordance with the priority, where the number of the units of the
user equipment are calculated by subtracting a number of the units
of the user equipment, which perform retransmission, from a total
number of the units of the user equipment, for which scheduling
coefficients are calculated. As explained in a modified example,
for the allocation of the radio resource, data which is for
retransmission has higher priority than that of data which is not
for retransmission.
[0044] A TFR (Transport Format and Resource) selector 211
determines a transport format (a data modulation scheme and a
channel coding rate) and a resource block for the user equipment,
to which a radio resource is to be allocated, based on a command
from the scheduler 207.
[0045] The downlink signal generator 213 generates a downlink
signal including a control signal and a data signal. The control
signal indicates how the radio resource is allocated to the user
equipment. For a case of an LTE-based mobile communication system,
the control signal includes at least a physical downlink control
channel (PDCCH). To be more precisely, the channel on which the
control signal is transmitted includes not only the PDCCH, but also
a PCFICH which is for transmitting a format indicator (CFI), and a
channel (PHICH) for transmitting acknowledgement information. Here,
the format indicator (CFI) indicates a number of OFDM symbols onto
which the PDCCH is mapped, and the acknowledgement information
indicates acknowledgement or non-acknowledgement with respect to an
uplink data signal (PUSCH) which is received by the eNodeB. The
control signal in the embodiment includes uplink or downlink grant
information. The uplink or the grant information includes a user's
identifier to whom the radio resource is allocated and information
regarding a resource block which is assigned in a downlink and/or
an uplink and a data format (a data modulation scheme and a channel
coding rate), for example. The data signal is mapped onto a
resource block which is specified by a control signal. The data
signal includes user data. In general, the data signal includes
voice data (VoIP), real-time data, and data for a data
communication, for example. For the case of the LTE-based mobile
communication system, a data signal corresponds to a physical
downlink shared channel (PDSCH) and a physical uplink shared
channel (PUSCH).
[0046] The downlink signal transmitter 215 transmits a downlink
signal which is generated by the downlink signal generator 213.
Thus, the downlink signal transmitter 215 includes a function to
apply channel coding to data to be transmitted; a function to apply
data modulation to the data to be transmitted; a function to
convert a digital signal into an analog signal; a function to
filter the signal to be transmitted; and a function to amplify the
signal to be transmitted, for example.
2. Operation Example
[0047] FIG. 3A and FIG. 3B are a flowchart showing an operation
example of the eNodeB such as shown in FIG. 2. The flow starts from
step S301, and the flow proceeds to step S303.
[0048] At step S303, the eNodeB determines priority of units of
user equipment, which are targets of scheduling. Specifically, the
units of the user equipment which are the targets of the scheduling
are the units of the user equipment that have data to be
transmitted on the uplink. The priority is determined in accordance
with a logical channel group LCG and a scheduling coefficient of
the data which is to be transmitted by the user equipment (UE). In
general, the priority of periodic data which is periodically
generated, such as voice data, is higher than the priority of
non-periodic data which is not generated at periodic timing. To be
more precise, a descending order of the priority corresponds to
periodic data to be retransmitted; non-periodic data to be
retransmitted; periodic data which is not for retransmission; and
non-periodic data which is not for retransmission. Further, the
priority is determined for each unit of user equipment that
transmits the periodic data or the non-periodic data, depending on
the scheduling coefficient. For simplicity of the explanation, the
explanation is given by considering a case where a user
communicates voice data as an example. However, the embodiment is
not limited to the voice data, and the embodiment can be applied to
a case where any periodically generated data is communicated. For
example, a PING signal may be used, which is periodically
transmitted for testing normality of a communication
connection.
[0049] At step S305, the eNodeB determines a voice user
multiplexing number N.sub.VOICE, depending on a number of units of
user equipment that transmit voice data among the units of the user
equipment which are located within a cell. The maximum voice user
multiplexing number N.sub.VOICE is set to be less than the maximum
user multiplexing number N.sub.MAX. The maximum user multiplexing
number N.sub.MAX is the maximum number of the units of the user
equipment that can transmit data on the same uplink subframe. The
maximum voice user multiplexing number N.sub.VOICE is the maximum
number of the units of the user equipment that can transmit
periodic data on the same uplink subframe. The voice user
multiplexing number N.sub.VOICE may be maintained to be constant,
regardless of the number of the units of the user equipment.
However, from a perspective of promoting the effective utilization
of the radio resources, it is preferable that the voice user
multiplexing number N.sub.VOICE is adjusted depending on a number
of users that communicate voice data.
[0050] In the following operation example regarding FIGS. 3A and
3B, it is assumed that the maximum user multiplexing number
N.sub.MAX is 3, and that the maximum voice user multiplexing number
N.sub.VOICE is 2.
[0051] At step S307, various types of parameters are initialized.
Specifically, a number of voice users I.sub.VOICE to whom radio
resources are allocated is set to be 0. Here, the voice users are
users who transmit voice data. A number of users I to whom radio
resources are allocated is also set to be 0. A value of priority m
is set to be 1. For the priority, 1 is the highest, and the
priority is lowered as the number is increased. At this time, the
values of the parameters are as follows.
[0052] Maximum user multiplexing number: N.sub.MAX=3
[0053] Maximum voice user multiplexing number: N.sub.VOICE=2
[0054] Number of allocated voice users: I.sub.VOICE=0
[0055] Number of allocated users: I=0
[0056] Priority: m=1
[0057] At step S309, the eNodeB selects the user equipment UE#x
having the mth highest priority. For the case of the current
example, since m=1, the user equipment UE#x1 having the highest
priority is selected. For example, when user equipment that
transmits voice data and user equipment that transmits data other
than the voice data coexist, the user equipment that transmits the
voice data is selected.
2.1 A Case where Voice Users and Non-Voice Users Coexist
[0058] For convenience of the explanation, suppose that seven units
of user equipment are targets of the scheduling. Further, suppose
that the units of the user equipment UE#x1-4 having the
corresponding priority m of 1-4 are the units of the user equipment
that transmit the voice data, and that the units of the user
equipment UE#x5-7 having the corresponding priority m of 5-7 are
the units of the user equipment that transmit the non-voice
data.
[0059] At step S311, the eNodeB determines whether a radio resource
is remaining, which can be allocated to the user equipment. When
the radio resource is remaining, the flow proceeds to step S313,
and when the radio resource is not remaining, the flow proceeds to
step S323.
[0060] At step S313, the eNodeB determines whether the data which
is transmitted by the user equipment UE#1x1 is the voice data (more
generally, periodic data). When it is the voice data, the flow
proceeds to step S315. For the case of the current example, since
the user equipment UE#x1 having the priority m=1 is the user
equipment that transmits the voice data, the flow proceeds to step
S315.
[0061] At step S315, the eNodeB determines whether the number of
the allocated voice users I.sub.VOICE is less than the maximum
voice user multiplexing number N.sub.VOICE=2. When the I.sub.VOICE
is less than N.sub.VOICE, the flow proceeds to step S317. When the
I.sub.VOICE is not less than N.sub.VOICE, the flow proceeds to step
S327. For the case of the current example, since I.sub.VOICE=0, the
flow proceeds to step S317.
[0062] At step S317, the number of allocated voice users
I.sub.VOICE is incremented, and I.sub.VOICE=1.
[0063] At step S319, the number of allocated users I is
incremented, and I=1. At step S321, the eNodeB determines a radio
resource to be allocated to the user equipment UE#x1 in the target
subframe and the transport format (the data modulation scheme and
the channel coding rate) to be used.
[0064] At step S323, the value m of the priority is incremented,
and m=2.
[0065] At step S325, the eNodeB determines whether the number of
allocated users I is less than the maximum user multiplexing number
N.sub.MAX. For the case of the current example, since I=1, the flow
returns to step S309. At this time, the values of the parameters
are as follows.
[0066] Maximum user multiplexing number: N.sub.MAX=3
[0067] Maximum voice user multiplexing number: N.sub.VOICE=2
[0068] Number of allocated voice users: I.sub.VOICE=1
[0069] Number of allocated users: I=1
[0070] Priority: m=2
[0071] At step S309, the eNodeB selects the user equipment having
the mth highest priority. For the case of the current example,
since m=2, the user equipment UE#x2 having the second highest
priority is selected.
[0072] At step S311, the eNodeB determines whether a radio resource
is remaining, which can be allocated to the user equipment. When
the radio resource is remaining, the flow proceeds to step S313,
and when the radio resource is not remaining, the flow proceeds to
step S323.
[0073] At step S313, the eNodeB determines whether the data to be
transmitted by the user equipment UE#x2 is the voice data (more
generally, periodic data). When it is the voice data, the flow
proceeds to step S315. For the case of the current example, since
the user equipment UE#x2 having the priority m=2 is the user
equipment that transmits the voice data, the flow proceeds to step
S315.
[0074] At step S315, the eNodeB determines whether the number of
allocated voice users I.sub.VOICE is less than the maximum voice
user multiplexing number N.sub.VOICE=2. For the case of the current
example, since I.sub.VOICE=1, the flow proceeds to step S317.
[0075] At step S317, the number of allocated voice users
I.sub.VOICE is incremented, and I.sub.VOICE=2.
[0076] At step S319, the number of allocated users I is
incremented, and I=2.
[0077] At step S321, the eNodeB determines a radio resource to be
allocated to the user equipment UE#x2 and the transport format (the
data modulation scheme and the channel coding rate) to be used.
[0078] At step S323, the value m of the priority is incremented,
and m=3.
[0079] At step S325, the eNodeB determines whether the number of
allocated users I is less than the maximum user multiplexing number
N.sub.MAX=3. For the case of the current example, since I=2, the
flow returns to step S309. At this time, the values of the
parameters are as follows.
[0080] Maximum user multiplexing number: N.sub.MAX=3
[0081] Maximum voice user multiplexing number: N.sub.VOICE=2
[0082] Number of allocated voice users: I.sub.VOICE=2
[0083] Number of allocated users: I=2
[0084] Priority: m=3
[0085] At step S309, the eNodeB selects the user equipment having
the mth highest priority. For the case of the current example,
since m=3, the user equipment UE#x3 having the third highest
priority is selected.
[0086] At step S311, the eNodeB determines whether a radio resource
is remaining, which can be allocated to the user equipment. When
the radio resource is remaining, the flow proceeds to step S313,
and when the radio resource is not remaining, the flow proceeds to
step S323.
[0087] At step S313, the eNodeB determines whether the data to be
transmitted by the user equipment UE#x3 is the voice data (more
generally, periodic data). When it is the voice data, the flow
proceeds to step S315. For the case of the current example, the
user equipment UE#x3 having the priority m=3 is the user equipment
that transmits the voice data, the flow proceeds to step S315.
[0088] At step S315, the eNodeB determines whether the number of
allocated voice user I.sub.VOICE is less than the maximum voice
data multiplexing number N.sub.VOICE=2. For the case of the current
example, since I.sub.VOICE=2, unlike the above-described cases, the
flow proceeds to step S327.
[0089] At step S327, the eNodeB determines whether there is user
equipment that transmits data other than the voice data, among the
units of user equipment, each of the units of the user equipment
having priority which is lower than that of the user equipment
having the mth highest priority. When such user equipment exists,
the flow proceeds to step S323, and when such user equipment does
not exist, the flow proceeds to step S317. For the case of the
current example, since the units of the user equipment (UE#x5-7)
exist which transmit the data other than the voice data, among the
units of the user equipment having priority which is lower than
that of the user equipment UE#x3 having the third highest priority,
the flow proceeds to step S323.
[0090] At step S323, the value m of the priority is incremented,
and m=4.
[0091] At step S325, the eNodeB determines whether the number of
allocated user I is less than the maximum user multiplexing number
N.sub.MAX=3. For the case of the current example, since I=2, the
flow returns to step S309. At this time, the values of the
parameters are as follows.
[0092] Maximum user multiplexing number: N.sub.MAX=3
[0093] Maximum voice user multiplexing number: N.sub.VOICE=2
[0094] Number of allocated voice users: I.sub.VOICE=2
[0095] Number of allocated users: I=2
[0096] Priority: m=4
[0097] At step S309, the eNodeB selects the user equipment having
the mth highest priority. For the case of the current example,
since m=4, the user equipment UE#x4 having the 4th highest priority
is selected.
[0098] At step S311, the eNodeB determines whether a radio resource
is remaining, which can be allocated to the user equipment. When
the radio resource is remaining, the flow proceeds to step S313.
When the radio resource is not remaining, the flow proceeds to step
S323.
[0099] At step S313, the eNodeB determines whether the data to be
transmitted by the user equipment UE#x4 is the voice data (more
generally, periodic data). When it is the voice data, the flow
proceeds to step S315. For the case of the current example, the
user equipment UE#x4 having the priority m=4 is the user equipment
that transmits the voice data, the flow proceeds to step S315.
[0100] At step S315, the eNodeB determines whether the number of
allocated voice users I.sub.VOICE is less than the maximum voice
user multiplexing number N.sub.VOICE=2. For the case of the current
example, since I.sub.VOICE=2, the flow proceeds to step S327.
[0101] At step S327, the eNodeB determines whether there exists
user equipment that transmits data other than the voice data, among
the units of the user equipment, where each of the units of the
user equipment has priority which is lower than that of the user
equipment having the mth highest priority. When such user equipment
exists, the flow proceeds to step S323, and when such user
equipment does not exist, the flow proceeds to step S317. For the
case of the current example, since there exist the units of the
user equipment (UE#x5-7) that transmit the data other than the
voice data, among the units of the user equipment having the
priority lower than that of the user equipment UE#x4 having the
fourth highest priority, the flow proceeds to step S323.
[0102] At step S323, the value m of the priority is incremented,
and m=5.
[0103] At step S325, the eNodeB determines whether the number of
allocated users I is less than the maximum user multiplexing number
N.sub.MAX=3. For the case of the current example, since I=2, the
flow returns to step S309. At this time, the values of the
parameters are as follows.
[0104] Maximum user multiplexing number: N.sub.MAX=3
[0105] Maximum voice user multiplexing number: N.sub.VOICE=2
[0106] Number of allocated voice users: I.sub.VOICE=2
[0107] Number of allocated users: I=2
[0108] Priority: m=5
[0109] At step S309, the eNodeB selects the user equipment having
the mth highest priority. For the case of the current example,
since m=5, the user equipment UE#x5 having the 5th highest priority
is selected.
[0110] At step S311, the eNodeB determines whether a radio resource
is remaining, which can be allocated to the user equipment. When
the radio resource is remaining, the flow proceeds to step S313,
and when the radio resource is not remaining, the flow proceeds to
step S323.
[0111] At step S313, the eNodeB determines whether the data to be
transmitted by the user equipment UE#x5 is the voice data (more
generally, periodic data). When it is the voice data, the flow
proceeds to step S315. For the case of the current example, unlike
the units of the user equipment UE#x1-3 having the corresponding
priority m=1-3, since the user equipment UE#x5 having the priority
m=5 is the user equipment that transmits the data other than the
voice data, flow proceeds to step S314.
[0112] At step S314, the number of allocated users I is
incremented, and I=3.
[0113] At step S321, the eNodeB determines the radio resource
allocated to the user equipment UE#x5 and the transport format to
be used (the data modulation scheme and the channel coding
rate).
[0114] At step S323, the value m of the priority is incremented,
and m=6.
[0115] At step S325, the eNodeB determines whether the number of
allocated user I is less than the maximum user multiplexing number
N.sub.MAX=3. For the case of the current example, since I=3, the
flow proceeds to step S329, and it is terminated.
[0116] As a consequence, the eNodeB generates uplink grant
information indicating that the radio resources are allocated to
the user equipment UE#x1 (voice user), the user equipment UE#x2
(voice user), and the user equipment UE#x5 (non-voice user), and
transmits it to the user equipment. The eNodeB receives uplink
signals which are transmitted by the units of the user equipment in
accordance with the uplink grant information.
[0117] FIG. 4 schematically shows an uplink subframe which is
transmitted by the units of the user equipment in accordance with
the uplink grant information. The uplink signal includes the voice
data of the user equipment UE#x1, the voice data of the user
equipment UE#x2, and the data other than the voice data of the user
equipment UE#x5. Unlike the conventional case, even if the number
of the units of the user equipment that transmit the voice data is
greater than the maximum voice user multiplexing number
N.sub.VOICE, the number of the voice users who are multiplexed in
the subframe is regulated to be the maximum voice user multiplexing
number N.sub.VOICE. Instead, the remaining radio resource is
allocated to the user equipment which transmits the data other than
the voice data. In this manner, by regulating the number of the
units of the user equipment which transmit the voice data to be
less than the maximum user multiplexing number N.sub.MAX, the
utilization efficiency of the uplink radio resources can be
improved.
2.2 A Case where Only Voice Users Exist
[0118] In the above-described example, the units of the user
equipment UE#x1-4 that transmit the voice data and the units of the
user equipment UE#x5-7 that transmits the data other than the voice
data coexist. When it is assumed that only the units of the user
equipment UE#x1-4 exist, the radio resources are allocated to the
units of the user equipment UE#x1-3. In such a case the flow
proceeds from step S327 to step S317.
[0119] To be more specific, the flow is as follows. First, the
radio resources are allocated to the user equipment UE#x1 of m=1
and to the user equipment UE#x2 of m=2 in the same manner as
described above, and the flow returns to step S309. At this time,
the values of the parameters are as follows.
[0120] Maximum user multiplexing number: N.sub.MAX=3
[0121] Maximum voice user multiplexing number: N.sub.VOICE=2
[0122] Number of allocated voice users: I.sub.VOICE=2
[0123] Number of allocated users: I=2
[0124] Priority: m=5
[0125] At step S309, the eNodeB selects the user equipment having
the mth highest priority. For the case of the current example,
since m=3, the user equipment UE#x3 having the 3rd highest priority
is selected.
[0126] At step S311, the eNodeB determines whether a radio resource
is remaining, which can be allocated to the user equipment. When
the radio resource is remaining, the flow proceeds to step S313,
and when the radio resource is not remaining, the flow proceeds to
step S323.
[0127] At step S313, the eNodeB determines whether the data to be
transmitted by the user equipment UE#x3 is the voice data (more
generally, periodic data). When it is the voice data, the flow
proceeds to step S315. For the case of the current example, since
the user equipment UE#x3 having the priority m=3 is the user
equipment that transmits the voice data, the flow proceeds to step
S315.
[0128] At step S315, the eNodeB determines whether the number of
allocated voice users I.sub.VOICE is less than the maximum voice
user multiplexing number N.sub.VOICE=2. For the case of the current
example, since I.sub.VOICE=2, the flow proceeds to step S327.
[0129] At step S327, the eNodeB determines whether there exists
user equipment that transmits data other than the voice data, among
the units of the user equipment, where each of the units of the
user equipment has priority which is lower than that of the user
equipment UE#x having the mth highest priority. When such user
equipment exists, the flow proceeds to step S323. When such user
equipment does not exist, the flow proceeds to step S317. For the
case of the current example, the user equipment having priority
which is lower than that of the user equipment UE#x3 having the 3rd
highest priority is only UE#x4, and this user equipment transmits
the voice data. Consequently, the flow proceeds to step S317.
[0130] At step S317, the number of allocated users I.sub.VOICE is
incremented, and I.sub.VOICE=3.
[0131] At step S319, the number of allocated users I is
incremented, and I=3.
[0132] At step S321, the eNodeB determines the radio resource which
is allocated to the user equipment UE#x3 and the transport format
to be used (the data modulation scheme and the channel coding
rate).
[0133] At step S323, the value m of the priority is incremented,
and m=4.
[0134] At step S325, the eNodeB determines whether the number of
allocated user I is less than the maximum user multiplexing number
N.sub.MAX=3. For the case of the current example, since I=3, the
flow proceeds to step S329, and it is terminated.
[0135] As a result, the eNodeB generates uplink grant information
indicating that the radio resources are allocated to the user
equipment UE#x1 (voice user), the user equipment UE#x2 (voice
user), and the user equipment UE#x3 (voice user), and the eNodeB
transmits it to the units of the user equipment. The eNodeB
receives uplink signals which are transmitted by the units of the
user equipment in accordance with the uplink grant information.
[0136] FIG. 5 schematically shows an uplink subframe that is
transmitted by the units of the user equipment in accordance with
such uplink grant information. The uplink signals include the voice
data of the units of the user equipment UE#x1-3. In this case, the
radio resource is remaining. However, since there is no user
equipment that transmits data other than the voice data, it is not
wasted so severely.
3. Modified Example
3.1 Modified Example where Retransmission is Considered
[0137] When the uplink radio resources are allocated to the units
of the user equipment in accordance with the priority, the priority
of the data to be retransmitted is higher than that of the data not
to be retransmitted. Accordingly, in general, the priority is
lowered in accordance with an order of first user equipment that
retransmits periodic data, second user equipment that retransmits
non-periodic data, third user equipment that transmits periodic
data which is not for retransmission, and fourth user equipment
that transmits non-periodic data which is not for retransmission.
When the eNodeB allocates radio resources to units of the user
equipment up to the maximum user multiplexing number N.sub.MAX, the
total number of the units of the first and third user equipment to
which the radio resources are allocated is regulated to be the
maximum voice user multiplexing number N.sub.VOICE, even if the
number of the units of the first and third user equipment is
greater than the maximum voice user multiplexing number
N.sub.VOICE.
[0138] In general, there are two types of retransmission. One of
them is such that a number of resource blocks for the
retransmission and a MCS (a combination of a data modulation scheme
and a channel coding rate) are specified by a control signal
(PDCCH), and the retransmission is performed by the specified ones.
For convenience, this method of retransmission is referred to as
"grant retransmission." For the case of the grant retransmission,
the user equipment receives the PDCCH, and subsequent to a
predetermined time period elapsing (for example, after 4 ms),
retransmission is performed by using the number of the resource
blocks and the MCS, which are specified by the PDCCH. The other
retransmission does not use the control signal (PDCCH). When the
user equipment receives acknowledgement information indicating the
non-acknowledgement (NACK) from the eNodeB through the control
signal (PHICH), subsequent to a predetermined time period elapsing
(for example, after 4 ms), retransmission is performed by using the
number of the resource blocks and the MCS, which are the same as
those of the previous time. For convenience, this retransmission
method is referred to as the "PHICH retransmission." Namely, for
the case of the PHICH retransmission, the eNodeB can inform the
user equipment to perform retransmission without using a PDCCH
resource. Namely, when the eNodeB allocates radio resources to
units of the user equipment up to the maximum user multiplexing
number N.sub.MAX in accordance with the priority, and when a radio
resource is allocated for the grant retransmission, it is necessary
to increase the number of allocated users I.sub.VOICE. Whereas, for
a case where a radio resource is allocated for the PHICH
retransmission, it is not necessary to increase the number of
allocated voice users I.sub.VOICE. That is because the number of
allocated voice users I.sub.VOICE can be said to be the number of
the voice users that use the PDCCH resources, in other words.
Accordingly, when the eNodeB allocates radio resources for the
PHICH retransmission of specific user equipment, radio resources to
be allocated to different user equipment can be specified by using
PDCCH resources, which are not utilized yet.
[0139] FIG. 6A and FIG. 6B show a flowchart of an operation
example, which is used in this modified example. It is
substantially the same as that of shown in FIG. 3A and FIG. 3B.
However, it is different in a point that step S601 is added. At
step S601, when data of user equipment UE#x is not to be
transmitted by the PHICH retransmission, the flow proceeds to step
S315, and the already explained processes are performed.
Specifically, the case other than the PHICH retransmission is a
case where it is the grant retransmission or it is not
retransmission. When the PHICH retransmission is performed, the
flow proceeds to step S319, and the number of allocated users I is
incremented, and the radio resources are ensured at step S321.
After that, the already explained processes are performed.
[0140] As described above, the user equipment transmits periodic
data such as voice data or non-periodic data by the grant
retransmission, the PHICH retransmission, or new transmission. As
shown in FIG. 7, suppose that first user equipment UE1 that
transmits periodic data by the grant retransmission, second user
equipment UE2 that transmits periodic data by the PHICH
retransmission, third user equipment UE3 that transmits periodic
data by new transmission, fourth user equipment UE4 that transmits
non-periodic data by the grant retransmission, fifth user equipment
UE5 that transmits non-periodic data by the PHICH retransmission,
and sixth user equipment UE6 that transmits non-periodic data by
new transmission exist. It is assumed that the priority in the
descending order is UE1, UE2, UE4, UE5, UE3, and UE6. In this case,
UE1, UE3, UE4, and UE6 use the PDCCH resource for allocation of the
radio resources. Since data of UE2 and UE5 are transmitted by the
PHICH retransmission, the PDCCH resource is not necessary. Suppose
that grant information for radio resources for three users can be
included in the PDCCH. In this case, in the uplink, the data of
UE1-5 can be multiplexed by using the PDCCH resource for UE1, UE3,
and UE5, and by performing the PHICH retransmission for the UE2 and
UE5
3.2 Modified Example where PDCCH Resource Allocation Amount is
Considered
[0141] The control signal for allocating the radio resource of the
downlink or the uplink shared channel is transmitted to each of the
units of the user equipment by the PDCCH. The PDCCH included in one
subframe (a unit transmission time period or a transmission time
interval TTI) may include control information which is addressed to
a plurality of units of the user equipment. In this case, the
amount of the PDCCH radio resource used for each of the units of
the user equipment is not necessarily the same. That is because the
amount of the radio resource which is required for maintaining the
receiving quality of the PDCCH (for example, a receiving error
rate) differs depending on a communication condition of each of the
units of the user equipment. For example, for a case of user
equipment located in the vicinity of the eNodeB, since the radio
channel condition is good, required quality can be satisfied even
if the channel coding rate is high. Thus, in this case, the amount
of the PDCCH radio resource can be small. Conversely, for a case of
user equipment at an edge of a cell, since the radio channel
condition is poor, the required quality may not be satisfied,
unless the channel coding rate is set to be low. Accordingly, in
this case, a large amount of the PDCCH radio resource is required.
For the case of the LTE-based mobile communication system, the
PDCCH radio resource is allocated to each unit of the user
equipment in a unit which is called a "control channel element
(CCE)." One CCE corresponds to nine resource element groups (REGs).
For example, as specific numbers of the CCE, 1(2/3), 2(1/3),
4(1/6), and 8( 1/12) are considered. The numbers in the brackets
are channel coding rates.
[0142] From such a perspective, instead of using the maximum user
multiplexing number and the maximum voice user multiplexing number
as in the explanation of the operation example, the units of the
user equipment to be multiplexed to the PDCCH may be determined by
considering the whole amount of the PDCCH radio resource and the
amount of the PDCCH radio resource for the voice users. This
modified example determines the units of the user equipment that
can use the shared data channel from such a perspective.
[0143] For example, suppose that three of OFDM symbols which are
included in one subframe are used for a control channel (CFI=3),
the system bandwidth is 5 MHz, and the number of REGs that can be
used for the PDCCH is 184. In this case, since 1 CCE=9 REGs, there
are 20 CCEs (184/9). Among these 20 CCEs, suppose that 12 CCEs are
allocated to voice users. Further, suppose that there are three
voice users (UE#A, UE#B, and UE#C), and that there are two data
communication users. UE#A, UE#B, and UE#E are located at an edge of
a cell, and eight CCEs are required. UE#C is located in the
vicinity of the eNodeB, and one CCE is good enough. UE#D is located
at a position which is separated from the eNodeB compared to the
vicinity of the eNodeB, but it does not reach the edge of the cell,
and four CCEs are required. Among these units of user equipment,
suppose that the priority in the descending order is UE#A, UE#B,
UE#C, UE#D, and UE#E.
[0144] FIG. 8 shows a situation of the specific example. In this
modified example, basically, it is attempted to allocate the PDCCH
radio resources in accordance with the descending order of the
priority. When the PDCCH radio resources are allocated, radio
resources of a shared data channel are allocated.
[0145] First, it is attempted to allocate the PDCCH radio resources
to the user equipment UE#A of a voice user having the priority m=1.
For the case of the user equipment UE#A, 8 CCEs are required. Since
this is less than the upper limit value of 12, the PDCCH radio
resources are allocated to the user equipment UE#A of the voice
user.
[0146] Next, it is attempted to allocate the PDCCH radio resources
to the user equipment UE#A of a voice user having the priority m=2.
The user equipment UE#B also requires 8 CCEs. However, the total
number of the CCEs for allocating the PDCCH radio resources to the
units of the user equipment UE#A and B is 8+8=16, and it exceeds
the upper limit value 12. Accordingly, the PDCCH radio resources
are not allocated to the user equipment UE#B of the voice user.
[0147] Next, it is attempted to allocate the PDCCH radio resource
to the user equipment UE#C of the voice user having the priority
m=3. For the case of the user equipment UE#C, one CCE is required.
The total number of the CCEs which are required for allocating the
PDCCH radio resources to the units of the user equipment UE#A and C
is 8+1=9, and it is less than the upper limit value of 12.
Accordingly, the PDCCH radio resource is allocated to the user
equipment UE#C for the voice user.
[0148] Next, it is attempted to allocate the PDCCH radio resources
to the user equipment UE#D of a data communication user having the
priority m=4. For the case of the user equipment UE#D, four CCEs
are required. The total number of the CCEs which are required for
allocating the PDCCH radio resources to the units of the user
equipment UE#A, C, and D is 9+4=13. Since the user equipment UE#D
is for a data communication user, the maximum number 20 of the CCEs
is considered. For the case of the current example, the total
number of the CCEs which are required for allocating the PDCCH
radio resources to the units of the user equipments UE#A, C, and D
is 13, and it is less than the upper limit value 20. Accordingly,
the PDCCH radio resources are allocated to the user equipment UE#D
of the voice user.
[0149] Finally, it is attempted to allocate the PDCCH radio
resources to the user equipment UE#E of a data communication user
having the priority m=5. For the case of the user equipment UE#E, 8
CCEs are required. The total number of the CCEs which are required
for allocating the PDCCH radio resources to the unit of the user
equipment UE#A, C, D, and E is 13+8=21, and it exceeds the upper
limit value 20. Accordingly, the PDCCH radio resources are not
allocated to the user equipment UE#E of the voice user.
[0150] In this manner, by regulating the PDCCH radio resources (the
number of the CCEs), which are allocated to the voice users, the
radio resources which are included in the subframe can be
effectively utilized.
[0151] FIG. 9A, FIG. 9B, and FIG. 9C show an operation example for
a case in which the radio resources are allocated to the user
equipment according to the modified example. In general, there are
steps which are the same as those of FIG. 3A and FIG. 3B, and those
of FIG. 6A and FIG. 6B. The same reference numerals are attached to
them. In the modified example, the PDCCH radio resources which are
allocated to the voice users are regulated to be less than or equal
to a constant amount. Thus, parameters which are different from
those of FIG. 6A and FIG. 6B are utilized. Specifically, at step
S901, the upper limit value (the number of the CCEs) P.sub.MAX,
VOICE, PDCCH of the PDCCH radio resource amount, which can be
allocated to the voice users, is set to be a specific value. The
value which is to be set may be a fixed value, similar to the case
of the voice user multiplexing number N.sub.VOICE, or the value may
be controlled to be varied, depending on the number of the voice
users in the cells. Further, the PDCCH radio resource amount (the
number of CCEs) I.sub.VOICE, PDCCH, which is actually allocated to
the voice user is set to be 0. The allocated PDCCH radio resource
amount (the number of CCEs) I.sub.PDCCH, which is actually
allocated irrespectively of whether it is the voice data or not, is
set to be 0. The value m of the priority is set to be 1.
[0152] In the modified example, for the case of the voice user, the
flow reaches step S601, and if it is not the PHICH retransmission,
the flow proceeds to step S905. For the case of the PHICH
retransmission, since the PDCCH radio resource is not utilized, the
flow proceeds to step S321, and the already explained processes are
executed.
[0153] At step S905, a determination is made as to whether the
PDCCH radio resource amount (the number of CCEs) I.sub.VOICE, PDCCH
which is actually allocated to the voice users is less than or
equal to the upper limit value (the number of CCEs) of the PDCCH
radio resource amount P.sub.MAX, VOICE, PDCCH which can be
allocated to the voice users. When it exceeds the upper limit
value, the flow proceeds to step S327, and the already explained
processes are executed. When it does not exceed the upper limit
value, the flow proceeds to step S907.
[0154] At step S907, a determination is made as to whether the
radio resource amount I.sub.VOICE, PDCCH which is required if the
PDCCH radio resources are to be allocated to the target units of
the user equipment, is less than or equal to the upper limit value
(the number of CCEs) P.sub.MAX, VOICE, PDCCH of the PDCCH radio
resources which can be allocated to the voice users. If the
required radio resource amount exceeds the upper limit value, the
flow proceeds to step S323, and the PDCCH radio resources are not
allocated to the target units of the user equipment. If the
required radio resource amount does not exceed the upper limit
value, the flow proceeds to step S909.
[0155] At step S909, the PDCCH radio resource amount (the number of
CCEs) I.sub.VOICE, PDCCH which is actually allocated to the voice
users is incremented by an amount which is allocated to the target
units of the user equipment.
[0156] At step S911, the PDCCH radio resource amount (the number of
CCEs) I.sub.PDCCH, which is actually allocated irrespectively of
whether the users are voice users, is incremented by an amount
which is allocated to the target units of the user equipment.
[0157] At step S323, the PDCCH radio resources are allocated to the
target units of the user equipment, and the radio resources of the
shared data channel are also ensured.
[0158] For the case where data is other than the voice data, the
flow reaches step S911.
[0159] At step S911, if it is not the PHICH retransmission, the
flow proceeds to step S913. For the case of the PHICH
retransmission, since the PDCCH radio resources are not utilized,
the flow proceeds to step S321, and the already explained processes
are executed.
[0160] At step S913, a determination is made as to whether the
radio resource amount I.sub.VOICE, which is required if the PDCCH
radio resources are allocated to the target units of the user
equipment, is less than or equal to the upper limit value (the
number of CCEs) P.sub.MAX, VOICE PDCCH of the PDCCH radio resource
amount which can be allocated regardless of whether it is the voice
user. When the required radio resource amount exceeds the upper
limit value, the flow proceeds to step S323, and the PDCCH radio
resources are not allocated to the target units of the user
equipment. When the required radio resource amount does not exceed
the upper limit value, the flow proceeds to step S915.
[0161] At step S915, the PDCCH radio resource amount (the number of
CCEs) I.sub.PDCCH, which is actually allocated to the users, is
incremented by an amount which is allocated to the target units of
the user equipment.
[0162] At step S323, the PDCCH radio resources are allocated to the
target units of the user equipment, and the radio resources of the
shared data channel are also ensured.
[0163] At step S917, a determination is made as to whether the
PDCCH radio resource amount (the number of CCEs) I.sub.PDCCH, which
is actually allocated to the users, is less than or equal to the
PDCCH radio resource amount P.sub.MAX, PDCCH. When the allocated
radio resource amount is less than or equal to the PDCCH radio
resource amount, the flow returns to step S309, and the already
explained processes are executed. When the allocated radio resource
amount is less than or equal the PDCCH radio resource amount, the
flow proceeds to step S919.
[0164] At step S919, a determination is made as to whether the
priority m which corresponds to the total number (number of units
of UE) of the units of the user equipment which request allocation
of the radio resources. When m is not equal to the number of the
units of the UE, the flow returns to step S901, and the already
explained processes are executed. When m=the number of the units of
the UE, the flow proceeds to step S329, and it is terminated.
[0165] By performing such operations, the voice user multiplexing
number can be regulated from the perspective of the PDCCH radio
resource.
[0166] Hereinabove, the present invention is explained by referring
to the specific embodiments. However, the embodiments are merely
illustrative, and variations, modifications, alterations and
substitutions could be conceived by those skilled in the art. For
example, the present invention may be applied to any suitable
mobile communication system that transmits and receives voice data.
Specific examples of numerical values are used in order to
facilitate understanding of the invention. However, these numerical
values are simply illustrative, and any other appropriate values
may be used, except as indicated otherwise. Specific examples of
the formulas have been used in order to facilitate understanding of
the invention. However, these formulas are simply illustrative, and
any other appropriate formulas may be used, except as indicated
otherwise. The separations of the embodiments or the items are not
essential to the present invention. Depending on necessity, subject
matter described in two or more items may be combined and used, and
subject matter described in an item may be applied to subject
matter described in another item (provided that they do not
contradict). For the convenience of explanation, the devices
according to the embodiments of the present invention are explained
by using functional block diagrams. However, these devices may be
implemented in hardware, software, or combinations thereof. The
software may be prepared in any appropriate storage medium, such as
a random access memory (RAM), a flash memory, a read-only memory
(ROM), an EPROM, an EEPROM, a register, a hard disk drive (HDD), a
removable disk, a CD-ROM, a database, a server, and the like. The
present invention is not limited to the above-described
embodiments, and various variations, modifications, alterations,
substitutions and so on are included, without departing from the
spirit of the present invention.
[0167] The present international application is based on and claims
the benefit of priority of Japanese Patent Application No.
2011-101948, filed on Apr. 28, 2011, the entire contents of which
are hereby incorporated by reference.
LIST OF REFERENCE SYMBOLS
[0168] 201: Uplink signal receiver [0169] 203: Uplink quality
measurement unit [0170] 205: User multiplexing number controller
[0171] 207: Scheduler [0172] 211: TFR selector [0173] 213: Downlink
signal generator [0174] 215: Downlink signal transmitter
* * * * *